Your "core" is a word that is used a lot these days without really any understanding of the muscles involved and how to use them.
Today I want to explain which muscles make up your core, where in the body they are found and how they are, or rather should, be used.
When most people talk about the core they are mainly referring to the stomach muscles which although not wrong does not give the complete picture.
For example there are many pieces of equipment out there that help to strengthen your stomach muscles and as part of their advertising they will talk about “building a stronger core.” This is partly true, but obviously it would be more accurate to say that it “helped towards building a stronger core” as if you just used this piece of equipment you would miss out the other muscles that make up the core.
The Importance of a Strong Core
When we talk about the core we are grouping different muscles together and it is these muscles that make a strong connection between our lower and upper body, the "core".
Having a strong core will make our bodies more resilient to the external forces that are applied to our bodies daily.
For example even pushing open or pulling open a door requires some core strength otherwise as our hand met with the door our upper body will collapse.
Sport is where it really helps to have a strong core: take rugby or American football, the amount of power and strength those guys need to push off tackles and to avoid serious injury is huge. Without good core strength the players would be injured very seriously by leaving their spines unprotected.
Which muscles make up the core?
Stomach:
1. Transverse abdominals: These are the deepest of the stomach muscles and are also considered as the most important for a strong core. They act like a big weight lifter’s belt that ultimately does the same job. They will help with flexing and twisting at the waist and they protect our organs, but their main job is to create a strong core link between upper and lower body (Marked in red on the first diagram).
2. Obliques: These muscles are positioned slightly to the sides of our waists and link all the way up to the rib cage. There are 4 in total, 2 each side and are made up of internal and external obliques. They will help with the core and movements involving twisting and tilting at the waist (Marked in purple in the second diagram).
3. Rectus Abdominus: The 6 pack: which sits on top of the other stomach muscles and down the centre from the rib cage to the pubis 
bone. Its main job is to keep the pelvis in line which in turn protects the spine, although many men will tell you that its main job is to attract the ladies (Marked in red in the second diagram).
Back:
4. Erector Spinae: These are in fact very small muscles that run up your whole spine on both sides. Whilst your body has full control of them they do do their job automatically, after all you don’t have to remind your upper body to stay upward when you are standing. These muscles tend to be very tight and weak outside of the normal range. That is why, if you have a weak core, it is these muscles that tend to take the brunt of it. Obviously their main job is to keep you upright but they also help with the twisting and bending of your trunk.
Hip:
5. Ilio-psoas: Also known as your hip flexor muscles. These are situated at the top front of your legs and help raise the upper leg upwards. They join in the top of the thigh and travel through your pelvis and onto your lower spine. These muscles are notorious for being short because of the amount of sitting we tend to do and as they join into the lower spine they can be a direct cause of lower back pain. As well as being strong these also need to be supple.
6. Glutius Maximus: Your bum muscles basically and one of the biggest muscles in your body. It plays a major part in moving the legs during running, walking etc and is very important for good posture, which in turn is essential for a strong core. These muscles tend to be very weak on most people and therefore should be worked on.
7. Glutius Medius and Minimus: Well it’s starting to sound like a Roman gathering but these are actually 2 more muscles found in your bum underneath you glutius maximus. They are much smaller and again seem to be generally weak in most people. In my opinion these muscles are loosely core related. However if they are not functioning correctly they can create a weakness in the core, especially through sideways movement of the upper body. Their main jobs are to take your leg out to the side and to rotate the whole leg outwards.
Legs:
8. Hamstrings: These are definitely not considered part of the core muscles, however you really should consider them a member as one of their smaller roles is to aid the movement of our torsos backwards. Whilst it doesn’t have a major role and is often overlooked, it should be added because of the affect it has on the core when it is tight. The tighter your hamstrings the bigger the negative influence on your core strength. A very important muscle to stretch.
More than just brute strength
You may be able to tell that there is more to a strong core than just strength. Well you are right, as there is no point in having the strength if your body can’t access it. We call this “muscle function” and it is built up of strength, suppleness and the ability to access this as and when the body needs it within a fraction of a second. The only way to achieve this is to build up the strength of the muscles previously mentioned, stretch them all as regularly as you can and then practise specific core exercises.
What are core exercises?
Core exercises don’t involve just building up the strength in your core muscles, they are more specific than that.
The exercises that train your core directly nearly always result in a force acting against your upper or lower body making them want to go their separate ways.
A good example of a core exercise are the hip twists when you twist your legs to one side it wants to pull your body up and arch your back. By training your core muscles you are able to perform this exercise without your upper body leaving the ground. There are hundreds of core exercises out there and variety is the key as your core should be trained from all directions as we live in a 3D world. Mix them up and don’t stay with the same routine for longer than 4 weeks.
I hope this has helped you to understand the core. If you still have unanswered questions then please add a comment or email me and I will try to answer them as quickly as I can. Keep an eye out for our core exercise section where we will add more and more core exercises as time goes by.
Good luck, be safe and stay healthy!